The present disclosure is related to an apparatus, a method, and a program for positioning an endoscope that identify the position of an endoscope within a lumen structure when the endoscope is inserted into a lumen structure having branching structures such as bronchial tubes to observe the lumen structure.
Recently, attention is being focused on techniques for observing or operating on lumen structures of patients, such as the large intestines and the bronchial tubes, using endoscopes. However, although endoscopes are capable of obtaining images in which the colors and textures of the interiors of lumen structures are clearly represented by use of imaging elements such as a CCD (Charge Coupled Device), these images are two dimensional representations of the interiors of the lumen structures. For this reason, it is difficult to understand what portion of the interior of the lumen structure is being represented by endoscope images. Particularly, because endoscopes for the bronchial tubes are thin and have narrow fields of view, it is difficult for the leading ends of such endoscopes to reach the target positions thereof.
Therefore, techniques for generating virtual endoscope images that approximate images which are actually obtained by an endoscope, employing three dimensional images obtained by tomographic imaging using a modality such as a CT (Computed Tomography) apparatus and an MRI (Magnetic Resonance Imaging) apparatus, are being proposed. The virtual endoscope images are employed as navigating images to guide an endoscope to a target position within a lumen structure. However, experience and technique are required to guide the leading end of an endoscope to a target position within a short period of time in the case that the lumen structure has paths that branch in multiple steps, such as the bronchial tubes.
For this reason, a method in which an image of a lumen structure is extracted from a three dimensional image, the image of the lumen structure and an actual endoscope image, which is actually obtained by performing imaging with an endoscope, are matched, and a virtual endoscope image for the current position of the endoscope is generated from the three dimensional image of the lumen structure, has been proposed (refer to Japanese Unexamined Patent Publication No. 2013-150650).
Meanwhile, it is important for an endoscope to be guided through a path that leads to a target position at branching positions within lumen structures, in order for the endoscope to reach the target position. For this reason, methods for identifying the current position of an endoscope by matching actual endoscope images of branching positions, which are obtained by the endoscope, and virtual endoscope images of branching positions, have been proposed (refer to PCT Japanese Publication No. 2013-517909, PCT Japanese Publication No. 2012-505695, and International Patent Publication No. WO2011/102012). According to the methods of PCT Japanese Publication No. 2013-517909, PCT Japanese Publication No. 2012-505695, and International Patent Publication No. WO2011/102012, the current position of an endoscope can be identified, and therefore the leading end of an endoscope can be easily guided to a target position.